The field of the invention is the field of optical lenses and lens assembly.
The field of optical lens design and construction has progressed rapidly with introduction of computer analysis, computer aided production of aspheric lens elements and molds for plastic lens elements, and optical measuring tools for ensuring that the lens elements are within specifications.
The prior art shows that a lens design combining number of lens elements can be produced wherein the lens elements are produced to within specifications on a number of parameters such as diameter, thickness, uniformity of index and uniformity index of refraction, surface curvature, centricity of the surface with respect to the perimeter of the element, and concentricity of the various lens element surfaces with respect to each other. Then, a number of lens elements are typically held together with a lens element holder to produce a finished lens. Typically, the lens element holder has an aperture therethrough for the passage of light through each lens element in turn, and interior dimensions of the lens element holder which are specified to hold the lens elements so that the centers of the various lens elements are held within the correct tolerance with respect to a center line through the lens. The various lens elements are typically held in a spaced apart relationship with each other by spacers.
Lens elements may formed from a single optical material which is transparent to the wavelengths of light for which they are designed, or from a combination of subelements which such as doublets, triplets, and quadruplets. The combinations of subelements typically have two surfaces with concave and convex surfaces matching each other, so that the subelements may be contacted together and affixed together with a thin layer of transparent adhesive. The subelements may be adjusted in physical adjustment to each other. For example, the diameters of the two subelements may be equal to within a certain tolerance, and the alignment is made by ensuring that the diameters of the two subelements line up to within a give tolerance.
A more accurate alignment is possible if the two subelements are adjusted in optical adjustment to each other. In an optical adjustment as defined in this specification, optical means are used to measure the location of the physical parameters of the subelements, such as the optical axis, and the two subelements are moved relative to each other until the optical axis of each element are parallel and as close as possible to each other. Such optical adjustments allow more accuracy in adjusting the optically important parameters of the combination than would be possible with physical adjustment according to their diameters.
All of the elements of the lens, spacers, and holders have to be made to within tight specifications for high quality lenses. The interior of the lens element holder is typically finished by grinding and polishing to achieve tighter tolerances. The edges of the lens elements are ground to achieve a tighter tolerance on the diameter. The spacer elements are ground. All of the operations to bring the tolerance tighter are expensive. Typically, if any of the lens elements, lens element holders, or spacers are out of specification, they are discarded. In this way, the prior art ensures that lenses constructed from a batch of imperfect parts will have a high probability of meeting specifications for the finished lens.
This application is related to U.S. application Ser. No. 10/361,299 filed the same date as the present application, and entitled xe2x80x9cMethod for assembling lens elementsxe2x80x9d, by Tomasz Momot and Adam Jacobs.
It is an object of the invention to provide a method for assembling a number M of spaced apart lens elements and contacted subelements together with a lens element holder into a finished lens, wherein the spacing between adjacent lens elements does not rely on a spacer elements.
It is an object of the invention to provide a method for assembling a number M of spaced apart lens elements together with a lens element holder into a finished lens, wherein alignment of each lens element does not rely on mechanical contact between the body of the lens element holder and each lens element.
It is an object of the invention to provide a group of N lenses, each of the N lenses comprising M lens elements and subelements, starting with M groups of at least N elements and subelements, wherein the lens elements and subelements have relaxed tolerances in their physical characteristics.
It is an object of the invention to provide a method for assembling a large plurality of parts into a plurality N of finished lenses, where each of the N lenses comprises M lens elements, and wherein the tolerances on each of the M lens elements may be greatly broadened.
It is an object of the invention to provide a method for assembling a plurality of parts into a plurality N of finished assemblies, where each of the N finished assemblies comprises M parts cooperating together in the same way to provide the same function, and wherein the tolerances on each of the M parts may be greatly broadened.
A lens is constructed by optically adjusting lens elements with respect to each other in a spaced apart relationship, then affixing the lens elements so adjusted adhesively to a lens element holder. The physical relationship of each lens element with each other lens element does not rely on physical contact between the lens elements and the lens element holder or spacer elements.
M batches of at least N similar optical elements, where each optical element is produced to a loose tolerance, may be selected into N groups by measuring pm characteristics of each optical element, and then computing a value that a group of M optical elements, one optical element drawn from each of the M batches would have if assembled together. The computation is continued until N groups of optical elements are selected, each group consisting of one optical element from each of the M groups of optical elements, and wherein no optical element is a member of more than one of the N groups of optical elements, and wherein the value for each group meets a criterion. M batches of at least N similar parts, where each part is produced to a loose tolerance, may be selected into N groups by measuring characteristics of each part, and then computing a value that a group of M parts, one part drawn from each of the M batches would have if assembled together. The computation is continued until N groups of parts are selected, each group consisting of one part from each of the M groups of parts, and wherein no part is a member of more than one of the N groups of parts, and wherein the value for each group meets a criterion.